Process for the preparation of 3-halo-and pseudohalo-alkylsilane esters

ABSTRACT

3-Halo- and pseudohalo-alkylsilane esters are prepared by reacting an allyl X compound or a compound containing an allyl X structure with a hydridosilane ester in the presence of an iridium catalyst prepared under specific conditions and/or the reaction medium containing a 0.01-100 mol % excess of the allyl X compound or compound containing the allyl X unit relative to the amount of hydridosilane ester reactant.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a process for the preparation of 3-halo- andpseudohalo-alkylsilane esters by addition of hydridosilane esters in thepresence of catalysts to the double bond of unsaturated aliphaticcompounds which contain, as reacting group, the allyl halide orpseudo-halide structural element with a terminal double bond.

3-Chloropropyltrialkoxysilane, Si-methyl-3-chloropropyldialkoxysilaneand Si,Si-dimethyl-3-chloropropylalkoxysilane in particular are used assilane coupling agents, for example for glass fibres, in the foundryindustry and as fillers for polymers. The 3-halo- orpseudohalo-alkylsilane esters of formula I in particular are importantkey products for the preparation of, for example, a variety ofmercapto-, amino-, methacryloyloxy- and acryloyloxy-functionalorganosilanes, which have grown in importance over recent years tobecome a branch of industry in their own right.

Consequently there have already been attempts in various ways to preparesuch products. Current industrial production exclusively employs atwo-stage procedure in which allyl chloride is hydrosilylated withtrichlorosilane or methyldichlorosilane, generally in the presence ofplatinum-based catalysts, with the respective chloropropylchlorosilane,which is obtained in yields of between 50 and 83%, being subsequentlyesterified.

These production processes which are currently practiced are highlymaterial- and plant-intensive but, despite their considerabledisadvantages, have to be employed given the lack of betteralternatives, since the products are urgently required.

For this reason it has already been proposed, to hydrosilylate allylchloride using trialkoxysilanes. This method employs various platinumcatalysts and it is possible to realize product yields from about 20 to45%. The reproducibility of certain yields, which are indicated as beingup to about 70%, is disputed. Belyakova et al, Zh. Obshch. Khim. 44(106) 1974, No. 11, 2439-2442, report on the detailed investigation ofthis reaction path employing platinum catalysis. Moreover, they describethe secondary reactions which occur and confirm product yields rangingfrom about 20 to 45%. In the presence of rhodium catalysts using themethods described in U.S. Pat. Nos. 3,296,291 and 3,564,266, the productyields are again below 40% and are accompanied by considerable secondaryreactions. In the presence of high concentrations of specific dimericiridium-halide-diene complex catalysts, in accordance with U.S. Pat. No.4,658,050, the yields determined by gas chromatography reach levels of75%; however, in preparative terms it is only possible to achieveproduct yields of 55-60%. Further, the by-products described byBelyakova et al occur in large amounts too. A striking additionaldisadvantage is the need to use such costly noble metal complexes in ahigh concentration. Leaving aside the cost factor, this also leads tointolerable impurity and waste problems. A need, therefore, continues toexist for a simple method of preparing 3-halo and pseudohalo-alkylsilaneesters at improved yields at reasonable cost.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a simplemethod of preparing 3-halo and pseudohaloalkylsilane esters in improvedyields at reasonable cost.

Briefly, this object and other objects of the present invention, ashereinafter will become more readily apparent, can be attained in amethod of preparing 3-halo- and pseudohalo-alkylsilane esters of formula(I): ##STR1## wherein R is an alkyl, a branched alkyl or a cycloalkylgroup having 1 to 18 carbon atoms, which may be halogenated;

R¹ is R or hydrogen;

R² is R, hydrogen, an aryl substituent or halogen;

R³ is the same as group R², with the R³ substituent being the same as ordifferent from the specific R² group selected;

R⁴ is a branched or unbranched alkyl group of 1 to 10 carbon atoms,optionally containing aliphatic ether groups;

X is a fluoride, chloride, bromide, iodide, cyanide, isocyanate,isothiocyanate or azido radical; and

n is 0, 1 or 2 by hydrosilation, which comprises: reacting a compound offormula (II): ##STR2## wherein X, R¹, R² and R³ are as defined above, ora compound containing the pseudohalide structure of formula (II) as acomponent, wherein one of R² or R³ represents a bond to a carbon atom ofthe remaining portion of the compound, with a hydridosilane ester offormula (III):

    HSiR.sub.n (OR.sup.4).sub.3-n                              (III),

wherein R, R⁴ and n are as defined above, in the presence of a catalystof a group VIII element or compound thereof in a reaction medium underthe conditions in which (i) the amount of compound of formula (II) orcompound containing formula (II) is present in a 0.01 to 100 mol %excess of the amount of compound of formula III and/or (ii) the catalystis prepared by stirring a 1/10 to 1/10,000 molar solution of elementalIr, a compound of Ir or a combination thereof in the reaction mediumwithout heating for at least 20 minutes, the catalyst having aconcentration of from 10⁻⁵ to 10⁻³ mol %, based on the hydridosilaneester employed, and then conducting the hydrosilation reaction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It has surprisingly now been found that the difficulties in synthesis of3-halo and pseudohaloalkylsilane esters can largely be avoided, and thatester products can be obtained in yields of up to 89% if, for thepreparation of the products of formula I by the catalyzedhydrosilylation of unsaturated aliphatic compounds, which contain as thereacting group allyl halide or a pseudohalide structural element havinga terminal double bond, each of formula II: ##STR3## wherein X, R¹, R²and R³ as defined above, with hydridosilane esters having the structureIII:

    HSiR.sub.n (OR.sup.4).sub.3-n                              (III),

wherein R, R⁴ and n are as defined above, (i) the reaction is conductedin the presence of elements and/or compounds from subgroup VIII of thePeriodic Table, where the reaction component of formula II, alone or ina mixture, always is in excess of from 0.01 to 100 mol %, preferablyfrom 0.1 to 10 mol %, relative to the reaction component of formula III,if desired in a from 5 to 95% strength by weight solution in an inertsolvent (suitable solvents include hydrocarbons), and/or (ii) the esterproduct of formula I, at from one-tenth to ten-thousandth molar solutionor suspension of elemental iridium and/or of compounds of iridium, isprepared by stirring for at least 20 minutes in the presence of acatalyst at a concentration of from 10⁻⁵ to 10⁻³ mol %, based on thehydrogensilane employed. The hydrosilylation can be carried out in amanner known per se.

For example, in a batchwise process the reaction components of formulaIII are introduced into the reactor as an initial charge, preheated to,for example, 70° C. and doped with the catalyst solution prepared inaccordance with the invention, and finally the reactant of formula II ismetered in with stirring, all the while controlling the exothermicity ofthe reaction. The reaction time to be employed is generally from 30 to180 minutes.

In a batchwise process, however, another advantageous mode of reactionis one in which the catalyst is preformed in situ in the mixture ofreaction components II and III or with excess II, then, in the lattercase, component III is added, and finally the reaction is performed byheating to the activation temperature while controlling the exothermicevolution of heat.

The preferred reaction temperature is from 70° to 130° C. If desired,the application of elevated pressure may be useful, preferably up to 40bar.

In the case of a continuous reaction procedure it is advantageous topremix the two reaction components of formulas II and III and thecatalyst preparation, if desired in the presence of from 20 to 75% byweight, based on the sum of reaction components, of hydrocarbons and/orof the product of formula I as medium, and to pass this mixture inliquid form, employing average retention times of from 10 to 50 minutes,through a reaction tube which is thermostated at from about 70° to 120°C. Both in the batchwise and in the continuous reaction procedure, thepresent process yields up to 89% of the products of formula I.

The crude products of formula I thus prepared by the present processcontain comparatively only few by-products, so that it may be possibleto avoid subsequent esterification since workup by distillation providessufficiently pure products, especially for the use of the estercompounds in the synthesis of aminosilanes.

If, however, it is desired to isolate particularly pure and neutralproducts of formula I, then it is advisable to carry out a simplesubsequent esterification of the crude products, which, because of theirpreparation, still contain residual acidity, by the work-up methodswhich are generally known per se for silicon esters, for example byaddition of some alcohol to neutralize the acidity, followed finally byfiltration.

Products of formula I which can be prepared with particular advantage bythe present process in contrast to the prior art procedures are thefollowing compounds:

3-Chloropropyltrimethoxy- and -triethoxysilane,

3-Chloropropylmethyldimethoxy- and -diethoxysilane,

3-Chloropropyldimethylmethoxy- and -ethoxysilane,

3-Chloropropyltris(2-methoxy)ethoxysilane,

3-Chloropropyltris(2-methoxyethoxyethoxy)ethoxysilane,

3-Chloropropyldimethyl-sec-butoxysilane,

3-Chloro-2-methylpropyltrimethoxysilane,

2-Chloromethylbutyltrimethoxysilane,

3-Chloro-2-chloromethylpropylmethyldiethoxysilane,

3-Chloro-2-chloromethylbutyltriethoxysilane,

3-Chloropentyldimethyl(2-ethyl)hexyloxysilane,

3-Fluoropropyltriethoxysilane,

3-Bromopropyltriethoxysilane,

3-Bromo-2-methylbutylmethyldimethoxysilane,

3-Iodopropyltriethoxysilane,

3-Iodo-2-methylpropyltriethoxysilane,

3-Cyanopropyltriethoxysilane,

3-Isocyanatopropyltriethoxysilane,

3-Azidopropyltriethoxysilane,

3,4-Dibromo-2,3-dimethylbutylmethyldimethoxysilane,

3-Bromohexyldimethylethoxysilane,

3-Chloroheptyltrimethoxysilane,

3-Azidoheptyldimethylmthoxysilane,

3,3-Difluoropropyltriethoxysilane,

3,3-Dichloropropyltrimethoxysilane,

3,3-Dichloro-2-methylpropyltrimethoxysilane,

3,3,3-Trifluoropropyltriethoxysilane,

3,3,3-Trichloropropyltrimethoxysilane,

3,3,3-Trifluoro-2-trifluoromethylpropyltriethoxysilane, and

3,3,4,4,4-Pentafluorobutyltriethoxysilane.

Starting materials which are suitable for carrying out the process ofthe invention and which have the structure of formula II include, inparticular, the following compounds:

Allyl fluoride,

Allyl chloride,

Allyl bromide,

Allyl iodide,

Allyl azide,

Allyl cyanide,

Allyl isocyanate,

Methallyl fluoride,

Methallyl chloride,

Methallyl bromide,

Methallyl iodide,

3Chloromethyl-1-butene,

3Chloro-2-methyl-1-butene,

3Bromo-2-methyl-1-butene,

3,4-Dichloro-1-butene,

3,4-Dibromo-1-butene,

3Fluoro-2-fluoromethyl-1-propene,

3Chloro-2-chloromethyl-1-propene,

3Chloro-2-chloromethyl-1-butene,

3Chloro--1-pentene,

3-Chloro-2-methyl-1-pentene,

3,3-Difluoro-1-pentene,

3Chloro-1-hexene,

3Bromo-1-hexene,

3Chloro-1-heptene,

3Azido-1-heptene,

3,4-Dibromo-2,3-dimethyl-1-butene,

4Bromo-3-chloro-3,4,4-trifluoro-1-butene,

3,3-Difluoro-1-propene,

3,3-Dichloro-1-propene,

3,3-Dibromo-1-propene,

3,3-Difluoro-2-methyl-1-propene,

3,3-Dichloro-2-methyl-1-propene,

3,3-Dibromo-2-methyl-1-propene,

3,3-Dichloro-2-methyl-1-butene,

3,4-Dichloro-2-methyl-1-butene,

3,4-Dibromo-1-butene,

3,4-Dibromo-2-methyl-1-butene,

3,3,3-Trifluoro-1-propene,

3,3,3-Trichloro-1-propene,

3-Bromo-3,3-difluoro-1-propene,

3-Chloro-2-trifluoromethyl-1-propene,

3,3,3-Trifluoro-2-trifluoromethyl-1-propene,

3,3,4,4,4-Pentafluoro-1-butene,

3,4-Dichloro-3,4,4-trifluoro-1-butene, and

4-Bromo-3-chloro-3,4,4-trifluoro-1-butene.

Using the starting materials of formula II, alone or in a mixture withthe other components of the hydrosilylation reaction, but always withexcess component of formula II, iridium and/or its compounds are treatedin accordance with the invention and thereby the catalytically activesolution or suspension is prepared. Examples of suitable iridiumcomponents include iridium black, the particularly preferred chloridessuch as iridium(III) chloride, iridium(III) chloride hydrate,iridium(IV) chloride hydrate, hexachloroiridic acid 6-hydrate. Suitableiridium compounds also include iridium(IV) oxide hydrate, potassiumhexachloroiridate(IV), potassium hexachloroiridate(III) 3-hydrate,tris(acetylacetonato)iridium(III) and iridium(III) oxalate, and complexcompounds of iridium, for examplecis-dichlorobis(ethylenediamine)iridium(III) chloride,pentaamminechloroiridium(III) chloride, chlorotris(norbornadiene)iridium(I), chloro-(1,5cyclooctadiene) iridium(I) dimer,chlorocarbonylbis(cyclooctene)iridium(I) dimer,bis(tricarbonylchloroiridium), octachlorooctacarbonyltetrairidium(I,II),dodecacarbonyltetrairidium,1,5-cyclooctadienebis(methyldiphenylphosphine)iridiumhexafluorophosphate, bis(triphenylphosphine)iridiumcarbonyl chloride,hydridochlorotris(triphenylphosphine)iridium(III),dihydridochlorotris(triphenylphosphine)iridium(III) andcarbonylhydridotris(triphenylphosphine)iridium.

The hydrogensilane esters of formula III which are employed ashydrosilylating reaction components include triethoxysilane,trimethoxysilane, triisobutoxysilane, hydrogenmethyldiethoxysilane or-dimethoxysilane, hydrogencyclohexyldiisopropoxysilane, andhydrogendimethylethoxy-, -octyloxy- or -2-butoxyethoxysilane.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified.

EXAMPLE 1

In a thermostat-heatable 4 l multi-necked flask equipped with stirrer,internal thermometer and reflux condenser, 12 mg (4·10⁻⁵ mol) ofiridium(III) chloride hydrate was added to a liquid mixture consistingof 625 g (2.6 mol) of 3-chloropropyltriethoxysilane as reaction medium,625 g (8.17 mol) of allyl chloride and 1250 g (7.6 mol) oftriethoxysilane as reaction components, over 40 minutes at roomtemperature under N₂. On subsequent heating, a weakly exothermicreaction commenced at about 70° C. during which the internal reactortemperature rose over the course of about 30 minutes, with refluxbecoming continually weaker, to 104° C., and fell back again to 94° C.over the course of a further 15 minutes. The mixture was held at 90° C.with the aid of the thermostat for another 30 minutes.

For work-up, first of all the slight excess of allyl chloride wasremoved by distillation, subsequently the chloride acidity, formedbecause of the secondary reaction, which amounted to a total of 0.92mol, was neutralized with an equimolar mixture of ethanol andtriethylamine; the remaining mixture was filtered, and finally theproduct was purified by vacuum distillation via a column.

A total of 2200 g of 3-chloropropyltriethoxysilane was obtained. Afterdeducting the quantity employed of 625 g, the yield is 1575 g. Thisamount is a yield of 86% based on the triethoxysilane employed.By-products isolated were about 40 g of propyltriethoxysilane and about140 g of tetra-ethoxysilane.

EXAMPLE 2

A solution of 14 mg of dihydrogen hexachloroiridate in 2 ml ofisopropanol was mixed into a solution of 610 g (7.94 mol) of allylchloride in 625 g (2.6 mol) of 3-chloropropyltriethoxysilane and themixture was stirred under inert gas at room temperature for one hour.The reaction mixture, together with 1250 g (7.6 mol) of triethoxysilane,was then metered continuously via a mixing nozzle in the liquid phaseinto a tubular reactor which is fitted with a jacket and N₂ -blanketedreflux condenser and is configured as a communicating tube, with anaverage retention time of from 35 to 40 minutes at 79° C. At the entrysite, boiling and vigorous reflux occurred. The crude product emergingin liquid form and the communicating overflow was no longer boiling.Work up was carried out as described in Example 1. 1630 g of3-chloropropyltriethoxysilane were obtained. This amount corresponds toa yield of 89% based on the triethoxysilane employed.

EXAMPLE 3

In a minilab pressure reactor of the TINYCLAVE type (BUECHI) with acapacity of 25 ml, 4 g of p-xylene, 4.2 g (0. 055 mol) of allyl chlorideand 8.2 g (0.05 mol) of triethoxysilane were mixed intensively with 0.16mg (10⁻³ mol %) of chloro-(1,5-cyclooctadiene)iridium(I) dimer at roomtemperature for one hour. The reaction mixture was then heated at 80° C.for 2 hours in a thermostat. Analysis by gas chromatography gave aproduct yield of 83% of 3-chloropropyltriethoxysilane.

EXAMPLE 4 (Comparison Example)

In analogy to Example 3, a homogeneous reaction solution of 4 g ofp-xylene, 3.8 g (0.05 mol) of allyl chloride (instead of 4.2 gcorresponding to 0.055 mol), 8.2 g (0.05 mol) of triethoxysilane and0.16 mg (10⁻³ mol %) of chloro-(1,5-cyclooctadiene)iridium(I) dimer werereacted without a relatively long mixing or storage time. Analysis bygas chromatography gave a product yield of only 61% of3-chloropropyltriethoxysilane.

EXAMPLE 5

In analogy to Example 1, a reaction mixture consisting of 585 g (2.6mol) of 3-chloroisobutylmethyldiethoxysilane, 739 g (8.17 mol) ofmethallyl chloride and 1022 g (7.6 mol) of hydrogenmethyldiethoxysilanewas reacted with 16 mg of chlorocarbonylbis(cyclooctene)iridium(I)dimer. The internal reactor temperature rose during this reaction from70° C. to 112° C. over the course of about 40 minutes. Theafter-reaction required about 1 hour. A chloride acidity of 1.04 mol wasproduced. A total of 1986 g of 3-chloroisobutylmethyldiethoxysilane wasobtained. After deducting the 585 g quantity of the silane compoundemployed in the reaction medium at its start, the yield of the silane is1400 g. This is a yield of 82% based on the methyldiethoxysilaneemployed. By-products found were isobutylmethyldiethoxysilane andmethyltriethoxysilane.

EXAMPLE 6

In analogy to Example 1 a reaction mixture consisting of 700 g ofp-xylene, 803 g (8.1 mol) of allyl mustard oil and 936 g (7.66 mol) oftrimethoxysilane was stirred at room temperature for 90 minutes with asolution of 22 mg of dihydrogen hexachloroiridate in 3 ml ofisopropanol, and the components were reacted at from 90° to 114° C. over160 minutes. The mixture was worked up by distillation to give 1539 g(91% yield based on the trimethoxysilane employed) of3-isothiocyanatopropyltrimethoxysilane

EXAMPLE 7

In analogy to Example 3, a mixture of 3 g of p-xylene, 5.3 g (0.055 mol)of 3,3,3-trifluoro-1-propene and 9.4 g (0.5 mol) ofcyclopentyldiethoxysilane was reacted in the presence of 0.1 mg ofiridium(III) chloride hydrate, after a mixing time of 70 minutes, at 83°C. over 180 minutes. Analysis by gas chromatography gave a product yieldof 77% of 3,3,3-trifluoropropylcyclopentyldiethoxysilane.

EXAMPLE 8

In analogy to Example 1, a reaction mixture consisting of 140 g ofp-xylene, 242 g (2 mol) of allyl bromide and 335 g (1.9 mol) ofhydrogendimethyl(2-butoxyethoxy)silane was reacted in the presence of 2mg of iridium(III) chloride hydrate. Work-up by distillation gave 432 gof 3-bromopropyldimethyl(2-butoxyethoxy)silane. This corresponds to apreparative yield of 77%, based on the hydrogendimethylsilane esteremployed.

EXAMPLE 9

In analogy to Example 6, a reaction mixture consisting of 640 g ofp-xylene, 680 g (8.17 mol) of allyl isocyanate and 1250 g (7.6 mol) oftriethoxysilane was reacted at from 76° to 92° C. over the course of 150minutes. Working up by distillation gave 1350 g of3-isocyanatopropyltriethoxysilane in addition to the trimer.

EXAMPLE 10

In analogy to Example 1 a reaction mixture consisting of 90 g ofp-xylene, 144.6 g (1.04 mol) of 3,4-dichloro-2-methyl-1-butene and 259 g(1 mol) of hydrogenethyldimethoxysilane was reacted in the presence of 1mg of iridium(III) chloride hydrate. Working up by distillation gave 197g of 3,4-dichloro-2-methylbutylethyldimethoxysilane. This corresponds toa preparative yield of 76%, based on the hydrogenethylsilane dimethylester employed.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A process for the preparation of a silanecompound of formula I: ##STR4## wherein R is an alkyl, a branched alkylor a cycloalkyl group having 1 to 18 carbon atoms, which may behalogenated;R¹ is R or hydrogen; R² is R, hydrogen, an aryl substituentor halogen; R³ is equal to R², with a given R³ substituent being thesame as or different from the specific R² group selected; R⁴ is abranched or unbranched alkyl group of 1 to 10 carbon atoms, optionallycontaining aliphatic ether groups; X is a fluoride, chloride, bromide,iodide, cyanide, isocyanate, isothiocyanate or azido radical; and n is0, 1 or 2 by hydrosilation, which comprises: reacting a compound offormula (II): ##STR5## wherein X, R¹, R² and R³ are as defined above, ora compound containing the pseudohalide structure of formula (II) as acomponent, wherein one of R² or R³ represents a bond to a carbon atom ofthe remaining portion of the compound, with a hydridosilane ester offormula (III):

    HSiR.sub.n (OR.sup.4).sub.3-n                              (III),

wherein R, R⁴ and n are as defined above, in the presence of a catalystof a group VIII element or compound thereof in a reaction medium underthe conditions in which (i) the amount of compound of formula (II) orcompound containing formula (II), alone or in a mixture, is present in a0.01 to 100 mol % excess of the amount of compound of formula III and/or(ii) the catalyst is prepared by stirring a 1/10 to 1/10,000 molarsolution or suspension of elemental Ir, a compound of Ir or acombination thereof in the reaction medium without heating for at least20 minutes, the catalyst having a concentration of from 10⁻⁵ to 10⁻³ mol%, based on the hydridosilane ester employed, and then conducting thehydrosilation reaction.
 2. The process of claim 1, wherein the amount ofcompound of formula (II) or compound containing formula (II) is presentin 0.1-10 mol % excess relative to the amount of compound of formula(III).
 3. The process of claim 1, wherein the compound of formula (II)or compound containing formula (II) is present as a 5-95% strength byweight solution in an inert solvent, in the silane ester product offormula (I) or combinations of the solvent with the silane ester offormula (I).
 4. The process of claim 3, wherein said solvent is ahydrocarbon solvent.
 5. The process of claim 1, wherein the reaction isconducted at a temperature of 70° to 130° C.
 6. The process of claim 1,wherein the reaction is conducted at an elevated pressure.
 7. Theprocess of claim 6, wherein the pressure ranges up to 40 bar.
 8. Theprocess of claim 1, wherein the reaction is conducted continuously. 9.The process of claim 1, wherein any halosilane or pseudohalosilanecompound formed in the reaction as a byproduct is esterified in a knownmanner.